Brunescent lenses and normal human lenses more than 70 years old exhibit red fluorescence due to a fluorophor with emission miximum at 672 nm under excitation by the 647.1 nm line of a krypton ion laser. The properties and mode of occurrence of this fluorophor suggest that its formation is highly pertinent to senile nuclear pathology. Laser raman optical dissection technique has been applied to measure the variation of the concentration of sulfhydryl along the visual axis of aging human lenses. The 647.1 nm line of a krypton ion laser was used to avoid interferenece due to fluorescence.